1. Field of the Invention
The present invention relates to an improved tape automated bonding method.
2. Description of the Related Art
Conventional heater heads for use in resistive thermal bonding are designed such that a heater section, which contacts a material to be bonded, is disposed at a lower portion of a metal head having a nearly U shape, and is caused to generate heat in a short period of time due to Joule heat generated by a current supplied thereto, whereby the material to be bonded is heated by the generated heat. As generation of the Joule heat is proportional to an electric resistivity, the material for such a heater head is selected from those having a high electric resistivity in order to improve the heat generating efficiency. In order to provide a uniform heating temperature instantaneously, on the other hand, it is desirable to use a material which has a high thermal conductivity and has such a property that a solder material (e.g., solder) for a material to be bonded is difficult to adhere.
In consideration of the aforementioned electric resistivity, thermal conductivity or adhesiveness, the material for the head is inevitably restricted to molybdenum (Mo), tungsten or the like. As the overall size of the heater is enlarged, there would be a variation in heat generation and heat radiation, thus making it difficult to provide a uniform heating temperature instantaneously (within several seconds) due to the characteristic of the thermal conductivity.
If such a head is used to bond a bump electrode of a semiconductor device to an external connecting lead by a TAB (Tape Automated Bonding) method, therefore, a variation in the heating temperature of a heater section of the head is likely to cause the bump electrode to be separated from the semiconductor device at that portion where the temperature is high and to cause the bump electrode to be separated from the external connecting lead due to insufficient connection therebetween at that portion where a temperature is low. This prevents uniform bonding between the bump electrode and the external connecting lead.